Synthetic decapeptide antagonist to gonadotropin releasing hormone (GnRH). It is marketed by Praecis Pharmaceuticals as Plenaxis. Praecis announced in June 2006 that it was voluntarily withdrawing the drug from the market.

Used in the palliative treatment of advanced prostate cancer. Abarelix is a luteinizing hormone agonist that results in suppression of testicular or follicular steroidogenesis.

Mechanism of action

Abarelix binds to the gonadotropin releasing hormone receptor and acts as a potent inhibitor of gonadotropin secretion.

Absorption

Following IM administration of 100 mg, abarelix is absorbed slowly with a mean peak concentration of 43.4 ng/mL observed approximately 3 days after the injection.

Volume of distribution

Not Available

Protein binding

96-99%

Metabolism

In vitro hepatocyte (rat, monkey, human) studies and in vivo studies in rats and monkeys showed that the major metabolites of abarelix were formed via hydrolysis of peptide bonds. No significant oxidative or conjugated metabolites of abarelix were found either in vitro or in vivo. There is no evidence of cytochrome P-450 involvement in the metabolism of abarelix.

Route of elimination

Not Available

Half life

13.2 ± 3.2 days

Clearance

Not Available

Toxicity

The maximum tolerated dose of abarelix has not been determined. The maximum dose used in clinical studies was 150 mg. There have been no reports of accidental overdose with abarelix.